Many different types of image capturing devices are available to capture images, such as still images or video. Some image capturing devices include a single image capturing source, such as a still image camera. Other image capturing devices include multiple image capturing sources. For example, many camcorders support both still pictures and videos, and users can press the shutter while shooting a video or can enable a special mode which records the regular frame-rate video and slower frame-rate still pictures. A stereo camera, or any multi-camera system, which is used to extract and reconstruct three-dimensional information from a pair of images, is another good example of a multiple image capturing source device.
Each image capturing source generates an image with color tone characteristics specific to the image capturing source. Differences in color tone characteristics between two different image capturing sources are particularly noticeable in comparing images captured of the same scene. The color tone differences exist between the two image capturing sources due to different reasons. For some applications, the color tone differences are intentionally introduced. For example, in some camcorders, the still pictures and the videos, once captured by a CMOS sensor, go through the different processing routines optimized for the characteristics of each to enhance the quality of the videos and the still pictures. When users want to print out a frame from the video, however, it is important to convert the color tones of the video into those similar to the still images. For other applications, the differences are unintentional since even the same CMOS image sensors produce a slightly different image due to the less-than-perfect manufacturing process or lighting condition. For a stereo camera or multi-sensor systems, the resulting images would have some color tone differences, and it is desirable to reduce them as much as possible. Therefore, the need for reducing the color tone differences from different image capturing sources is demanded in many applications.